Part 2, 1917] AGARICACEAE 103 
I. SPECIES OCCURRING IN TEMPERATE NORTH AMERICA, EXCEPT THOSE CONFINED TO THE 
PaciFIC COAST 
Pileus uniformly white or varying to yellowish-white or grayish-white. 
Stipe 2-4 mm. thick. ae 
Stipe 2.5-3.5 em. long. 
Spores subglobose, 4~5 yu. 1, P. Underwoodii. 
_ Spores ellipsoid, 10-12 x 6-7 yu. 2. P. subplanus. 
Stipe 5-7.5 em. long. 
Pileus 1.5~2.5 em. broad. 3. P. lignicola. 
Pileus 2.5-5 em. broad, 4. P. Woodianus. 
Stipe 4-10 mm. thick. 
Hymenopbores cespitose. 5. P. caespitosus. 
Hymenophores not cespitose. 
Context having a strong odor of melilot. 6. P. Melilotus. 
Context having a farinaceous odor. 
Pileus segular with central stipe; species found in woods. 7. P. prunulus, 
Pileus irregular with eccentric stipe; species found in pastures 
: . and open places. 8. P. obesus. 
Pileus whitish with disk reddish-yellow or rusty. 9. P. noveboracensis. 
Pileus white with a dark-lilac tint. 10. P. Seymourianus. 
Pileus ochraceous. ll. P. depressus. 
Pileus pale-cinereous. 
Pileus 1-3 cm. broad. 
Lamellae adnate or slightly decurrent. 12, P. albogriseus. 
Lamellae long-decurrent. 13. P. subcinereus. 
Pileus 4 cm. broad. 14, P. cinereicolor. 
Pileus murinous. 15. P. murinus. 
Pileus at first bluish, becoming pale-purple or mauve. 16. P. washingtoniensis 
Pileus gray, grayish-brown, or avellaneous. 
Pileus 1-3.5 cm. broad. 
Stipe 1 cm. long. 17. P. magnisporus. 
Stipe 2.5 cm. long. 
Stipe 2 mm. thick; spores ellipsoid. 18. P. unitinctus. 
Stipe 2-4 mm. thick; spores subglobose. 
Hymenophores closely gregarious, 1-2 cm. broad. 19, P. socialis. 
Hymenophores not closely gregarious, 3-5 em. broad. 20. P. micropus. 
Stipe 7.5-10 cm. long. 21. P. squamulosus. 
Pileus 5-10 em. broad. 22. P. abortivus. 
Pileus reddish or pale-alutaceous, 5-7.5 em. broad. 23. P. pascuensis. 
Pileus reddish-brown, 2.5 em. broad. 24, P. irregularis. 
Pileus grayish-incarnate; context incarnate. 25. P. erythrosporus. 
Pileus chestnut-colored, black on the disk. 26, P. Lepionia. 
Pileus dark-gray or blackish-brown. 27. P. sphaerosporus. 
II. SpPEcIES CONFINED TO THE PACIFIC COAST 
Pileus white, 1-1.5 em. broad. 28. P. adnatifolius. 
Pileus avellaneous, 2.5-3.5 em. broad. 29. P. avellaneus. 
III. SPECIES OCCURRING IN TROPICAL NORTH AMERICA : 
Pileus white, 1-2 em. broad. 30. P. Earlei. 
Pileus gray, 5-10 cm. broad. 22. P. abortivus. 
1. Pleuropus Underwoodii (Peck) Murrill. 
Clitopilus Underwoodii Peck, Ann. Rep. N. Y. State Mus. 49: 32 (18). 1897. 
Pileus rather thin but fleshy, nearly plane or slightly depressed at the center, 1-3.5 cm. 
broad; surface even, whitish; lamellae narrow, crowded, slightly decurrent, pale-flesh-colored; 
spores subglobose, 4-5 #; stipe rather short, equal or slightly tapering upward, solid, whitish, 
about 2.5 em. long and 4 mm. thick. 
Type Locality: Syracuse, New York. 
Hasrrat: On the ground under coniferous trees. 
DISTRIBUTION: Known only from the type locality. 
2. Pleuropus subplanus (Peck) Murrill. 
Clitopilus subplanus Peck, Bull. N. ¥. State Mus. 122: 18. 1908. 
Pileus thin, broadly convex or nearly plane, slightly depressed at the center or distinctly 
umbilicate, 2.5-3.5 em. broad; surface glabrous, whitish or grayish-white; context white; spores 
ellipsoid, flesh-colored, angular, uninucleate, 10-12.5 X 6—-7.5 mu; stipe slender, glabrous, terete 
or compressed, stuffed or hollow, concolorous, 2.5~3.5 cm. long, 2-4 mm. thick. 
YPE LOCALITY: Sandlake, New York. _ . 
Eien Among fallen leaves and decaying vegetable matter in woods. 
DistRIBUTION: Northern New York. 
